Ionic Equilibria

What is the approximate pH of a solution labeled 6 x 10^-5 M HBr?

• 4.2

• 4.5

• 5.8

• 9.8

A solution in which [H⁺] = 10^-8 M has a pH of ___ and is ___.

• 8, acidic

• 6, acidic

• 8, basic

• 6, basic

What is the pH of 500 mL of solution containing 0.0124 grams of Ca(OH)₂ ? (RMM = 74)

• 3.8

• 10.2

• 3.2

• 10.8

In a sample of pure water, only one of the following statements is always true at all conditions of temperature and pressure. Which one is always true?

• [H₃O⁺] = 1.0 x 10^-7 M

• pH = 7.0

• pOH = 7.0

• [H₃O⁺] = [OH^-]

If K_w is 2.9 x 10^-15 at 10^oC, what is the pH of pure water at 10^oC?

• 6.72

• 7.00

• 7.27

• 7.53

Which of the following is true about a 0.10 M solution of a weak acid, HX?

• [X^-] = 0.10 M

• [H⁺] = 0.10 M

• pH = 1

• [HX] > [H⁺]

Which of the following solutions has the lowest pH at 25^oC? (No calculations required.)

• 0.2 M benzoic acid, Ka = 6.3 x 10^-5

• 0.2 M methanoic acid, Ka = 1.8 x 10^-4

• 0.2 M carbonic acid, Ka = 4.4 x 10^-7

• 0.2 M hypochlorous acid, Ka = 2.9 x 10^-8

Which of the following solutions has the highest pH at 25^oC? (No calculations required.)

• Ammonium ion, Ka = 5.8 x 10^-10

• Hydrogen sulfate ion, Ka = 1.0 x 10^-2

• Hydrogen carbonate ion, Ka = 4.7 x 10^-11

• Hydrogen phosphate ion, Ka = 4.2 x 10^-13

The pH of a 0.02 M solution of an unknown weak acid is 3.7. what is the pK_a of this acid?

• 4.9

• 5.7

• 3.2

• 2.8

A 0.10 M solution of a weak acid, HX, is 0.059% ionized. Calculate K_a for the acid.

• 3.8 x 10^-9

• 4.2 x 10^-6

• 3.5 x 10^-8

• 6.5 x 10^-7